In pregnant female rat, the cyclooxygenase inhibitor; flunixin meglumine administered intramuscularly in the therapeutic dose and its two fold evoked red patches on different parts of the body. The most frequently observed internal malformations in response to flunixin meglumine injection (0.4 mg/kg B.wt.) were dilated brain ventricles, thickening of the ventricular wall of the heart and dilatation of the renal pelvis. Flunixin meglumine injection at a dose of 0.8 mg/kg B.wt. evoked dilated brain ventricles, cerebral, intrathoracic and abdominal haemorrhages, marked thickening of ventricular wall of the heart and dilatation of renal pelvis. Skeletal malformation or response to both doses of the drug were absence of last caudal vertebrae, pronounced rudimentary or missing sternebrae and xiphisternam and absence of phalanges of both fore and hind limbs.